陕北槽齿类新发现

本文记述了采自陕北府谷县三迭系和尚沟组上部的一槽齿类化石。根据骨髂形态特征认为属于古鳄亚目的原鳄科,与Chasmatosaurus和Elaphrosuchus相近,但上颌骨参与外鼻孔的构成及前上颌骨不呈喙嘴状等却显著不同。为此另建立一新属(Xilousuchus)。考虑其一些进步的构造、新属种的生存时代应稍晚于上述Chasmatosaurus和Elaphrosuchus。

THE DISCOVERY OF A NEW THECODONT FROM NORTH-EAST SHENSI

The material dealt with in the present paper includes some imperfect and scattered bones of the skull, 12 vertebrae, a left clavical and several fragments of rib. It was excavated from a lower Triassic red sandy marl of He Shang-gou formation in the Ha Zhen commune of Fu Gu county in the north-east of Shensi Province during the autumn 1977. The new form named as Xilousuchus is closely related to Chasmatosaurus and Elaphrosuchus, and represents a new member of Proterosuchidae.The diagnosis of the new genus is as follows:Medium-sized proterosuchian with long neck and long tail. Skull lightly built, high, narrow and elongated. Premaxilla probably projecting forwards beyond lower jaw, but undeveloped and not bent downwards at tip to form "rostrum". A notch or concavity present at the lower border of skull between premaxilla and maxilla; maxilla joined in the border of narial opening, with a delecate branch; external naris unusually large and terminal in position; single, fairly antorbiral fenestra; paroccipital process contracted medially and expended distally. Lower jaw slender and upper margine of dentary curved, with hammer-like articular; retroarticular process developed moderately. Marginal teeth regularly isodont, 6(?) in premaxilla, 14 in maxilla, 13 in dentary. Clavicle scimiter-like. Cervical vertebra elongated without intercentra, dorsals with conciderablly high neural spine. No dermal armour.Remark: There are obviouly some advanced features in the new genus, such as: maxilla joined in the border of narial opening, cervical vertebra without intercentra, ect. According to the advanced characters, the age the animal lived at is probably a bit later than that of Cha. and Ela., which are from Lystrosaurus Beds. So it is reasonable that He Shang-gou formation that yields this specimen should be considered the de- posits in the early Triassic period, which is overlain by Eh mar-ying series from which many Kannemeyrids were found.